$15\mathrm{.}7$ C#$($MDI Text Editor$)$ Create an MDI text editor. Each child window should contain a multiline TextBox. The MDI parent should have a Format menu with submenus to control the size, font and color of the text in the active child window. Each submenu should have at least three options. In addition, the parent should have a File menu with menu items New $($create a new child$),$ close $($close the active child$)$ and Exit $($exit the app$).$ The parent should have a Window menu to display a list of the open child windows and their layout options.